I've posted some details before about the science of coagulation in terms of the casein micelle, how the enzyme chymosin acts on the micelle, the formation phases of a curd matrix, flocculation timings, and so on. But I think a lot of it has been overly technical. I found a video that does a great job in covering coagulation, and also provides an illustration for what happens at the biochemical level.

Some highlights are:

1) Uneven action of chymosin in cleaving not only k-casein but also the underlying a&b casein can lead to bitterness. This is part why using too much rennet can cause bitterness. The other reason is the too-rapid proteolytic action during aging when too much rennet remains with the curd.2) The end of phase 1, which coincides with the flocculation point, is when most of the k-casein shell has been cleaved and when the matrix starts to form because the micelles can attach to each other.

Thanks for all the educational postings! The more I understand, the more (I hope) I'll be able to expand my repertoire.I'm into a more natural approach myself- only use raw fresh milk- so probably wouldn't use that product.Pam

For acid coagulated cheeses that don't use rennet, coagulation happens because of the acid. The micelle has the outer layer of k-casein which likes water (hydrophilic) and stays in suspension because it has an electrical charge. When the pH gets low enough, to 4.6, that charge is no longer there, and the micelles drop out of suspension, making curd. That pH level of 4.6 in milk is also called the isoelectric point.

Sailor, I'm going to buy directly from CHR Hansen. They have an office in Wisconsin. I think the smallest size is 1 gal.

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Sure, I think I'll just split up a gallon into 32, 4 oz dropper bottles for convenience, and send them out to anyone who wants to try. I'll follow good aseptic lab procedures to ensure there's no contamination. No idea of cost right now, but it'll be cost of the rennet+bottle+shipping. Probably will wind up somewhere in the $3-$5 range+ shipping. I'll follow up in a few weeks with a new post after I get it all sorted out.

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Sailor, in general Aspergillus-fermented rennet has a very stable and long life. At 2 C you can expect 4-5% degradation/year. That's better than animal rennet, and about the same as regular m. miehei-derived rennet. I haven't read the product spec yet (not available), so I may not be exactly correct.

I got in touch with my CHR Hansen rep and she said Chymax-M is not available for general distribution yet. I think they're still building their production line. I'll try and bribe her in exchange for a small sample. No kidding, I've sent cookies before as a "bribe" (I called it a thank-you) with another company and it totally worked. . I'll let you know.

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Taking an extended leave (until 2015) from the forums to build out my farm and dairy. Please e-mail or PM if you need anything.